PHILADELPHIA (AP) — Philadelphia Phillies rookie infielder Freddy Galvis was suspended 50 games by Major League Baseball on Tuesday for testing positive for a banned substance.

Galvis is currently on the disabled list with a back injury and will begin serving his suspension immediately. MLB said Galvis tested positive for a metabolite of Clostebol, a performance-enhancing substance.

"A trace amount of a banned substance — 80 parts in a trillion — was detected in my urine sample," Galvis said in a statement. "I am extremely disappointed in what has transpired. I cannot understand how even this tiny particle of a banned substance got into my body.

"I have not and never would knowingly use anything illegal to enhance my performance. I have always tried to follow the team's strength and conditioning methods, listen to the trainers, work out hard and eat right. Unfortunately, the rules are the rules and I will be suspended."

Galvis, listed at 5-foot-10 and 170 pounds, had filled in nicely for injured second baseman Chase Utley before getting hurt. He was batting .226 with three homers, 15 doubles and 24 RBIs. It's likely Galvis will be on the DL for the duration of his suspension.

"It's disappointing," Phillies general manager Ruben Amaro Jr. said. "We fully support the program and the decision. At the same time, we support the player, we want him to get healthy and get back on the field. We believe in the kid and think he has a great future for us."

Galvis was primarily a shortstop in the minors and likely would've started at Triple-A this year because former MVP Jimmy Rollins plays his position. But Galvis moved over to second base in spring training to replace Utley and he made the transition look easy with his outstanding glove work.

The 22-year-old Galvis suffered a pars fracture of his L45 vertebra while swinging the bat during a game against the Los Angeles Dodgers on June 6. He is wearing a brace for at least three weeks and can't do any physical activity.

I'd like to apologize to my all my fans, especially here in Philadelphia and back home in Venezuela, to my teammates and to the Phillies organization," Galvis said. "I am looking forward to putting this behind me, rehabilitating my back and returning to the Phillies as soon as possible to try to help them win another World Series."